Fracture behavior of a high pressure die casting AlSi10MnMg alloy with varied porosity levels

Abstract

The fracture behavior of a high pressure die casting AlSi10MnMg alloy with varied porosity levels is investigated by synchrotron radiation X-ray computed tomography. Attention is focused on origin of crack and the evolution of porosity in the process of plastic deformation. Different from in-situ 3D tensile test, load-off specimen after plastic deformation is applied for this experiment and it is closer to the real scene. Results show that multiple defects are proposed in high pressure die casting AlSi10MnMg alloy including shrinkage, gas pore, externally solidified primary iron-rich phase (ESC-IMCI) and heterogeneous layers. In a lower-porosity sample, the surface defects like skin layer are a main crack source and a radial river pattern exhibits in crack surface. No new pores generated in the process of plastic deformation. In a higher-porosity sample, no obvious crack source and radial crack propagation path can be identified while the large crack surface fluctuation and tortuous morphology are obtained. The collapse of pre-existing small-sized pores exert a vital role in connecting large-scale pores. The micro-crack initiation and propagation originate from the expansion, consolidation and collapse of pores, especially the irregular pores.